1. Field of the Invention
The present invention relates to a back-illuminated solid-state imaging device, a method of making the same, and an imaging apparatus including the solid-state imaging device.
2. Description of the Related Art
Referring to FIG. 8, a back-illuminated solid-state imaging device includes a silicon substrate 211, in which photodiodes 221 are arranged, and a signal circuit section 231. Light is incident on a first surface of the silicon substrate 211. The signal circuit section 231 is arranged in a second surface of the silicon substrate 211. Assuming that the thickness of a silicon layer in a portion corresponding to each photodiode 221 is several micrometers or less, incident light components having long wavelengths are not sufficiently absorbed by the photodiodes 221 and are transmitted to the signal circuit section 231 in the second surface of the silicon substrate 211. Particularly, light components having long wavelengths (e.g., red wavelengths) are transmitted in a portion corresponding to each photodiode 221 and the transmitted light components enter the signal circuit section 231. Disadvantageously, it is difficult to efficiently convert light in a long wavelength range (hereinafter, long-wavelength light) into an electrical signal. Furthermore, the transmitted light is reflected by an interconnection laminate 233 in the signal circuit section 231, so that the reflected light is incident on the photodiodes in surrounding pixels, leading to crosstalk. Unfortunately, the occurrence of crosstalk causes a problem. For example, Japanese Unexamined Patent Application Publication No. 2006-261372 discloses a related-art solid-state imaging device having a structure in which a polysilicon layer and an aluminum layer are arranged on photodiodes. In this structure, it is insufficient to shield against long-wavelength light components, such as infrared light and near-infrared light. Particularly, the amount of transmitted light in the polysilicon layer is large. The aluminum layer is formed by grain growth. Disadvantageously, light is leaked from grain boundaries, thus reducing the reflectance.